nixos-config/configuration.nix

{ config, pkgs, lib, ... }:

{
  imports =
    [ 
      ./hardware-configuration.nix # Generated by the installer
      ./system-utils.nix           # CLI Tools
      ./user-apps.nix              # GUI Apps
    ];

  # ==========================================
  # 1. BOOT & KERNEL STRATEGY
  # ==========================================
  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;

  # --- KERNEL PARAMETERS (LLM/AI) ---
  # Force AMD GTT to 32GB. 
  # Combined with 16GB BIOS VRAM, this gives ~48GB total addressable to iGPU.
  boot.kernelParams = [ "amdgpu.gttsize=32768" ];
  
  # Load AMDGPU drivers early to prevent blank boot screens on Strix Point
  boot.initrd.kernelModules = [ "amdgpu" ];

  # --- DEFAULT MODE (Balanced/Daily Use) ---
  boot.kernelPackages = pkgs.linuxPackages_latest;

  # --- SPECIALISATIONS (Selectable at Boot) ---
  specialisation = {
    # Option 1: Gaming Mode (Zen Kernel + Max Performance)
    gaming-zen.configuration = {
      system.nixos.tags = [ "Gaming-Zen" ];
      boot.kernelPackages = lib.mkForce pkgs.linuxPackages_zen;
      hardware.nvidia.powerManagement.finegrained = lib.mkForce false; 
    };

    # Option 2: Eco/Battery Mode (TLP + No Turbo)
    battery-saver.configuration = {
      system.nixos.tags = [ "Eco-Battery" ];
      services.power-profiles-daemon.enable = lib.mkForce false;
      services.tlp = {
        enable = lib.mkForce true;
        settings = {
          CPU_SCALING_GOVERNOR_ON_BAT = "powersave";
          CPU_ENERGY_PERF_POLICY_ON_BAT = "power";
          CPU_BOOST_ON_BAT = 0;
          PLATFORM_PROFILE_ON_BAT = "low-power";
        };
      };
    };

    # Option 3: Expansion Shell (Physically Removed GPU)
    no-dgpu.configuration = {
      system.nixos.tags = [ "No-dGPU" ];
      
      # 1. Force Video Driver to standard modesetting (ignores Nvidia)
      services.xserver.videoDrivers = lib.mkForce [ "modesetting" ];

      # 2. Blacklist Nvidia Kernel Modules to prevent loading attempts
      boot.blacklistedKernelModules = [ "nvidia" "nvidia_modeset" "nvidia_uvm" "nvidia_drm" ];

      # 3. Disable Nvidia Hardware Options
      hardware.nvidia = {
        modesetting.enable = lib.mkForce false;
        powerManagement.enable = lib.mkForce false;
        open = lib.mkForce false;
        nvidiaSettings = lib.mkForce false;
        prime.offload.enable = lib.mkForce false;
      };
    };
  };

  # ==========================================
  # 2. NETWORKING & LOCALES
  # ==========================================
  networking.hostName = "electra"; 
  networking.networkmanager.enable = true;
  
  time.timeZone = "Europe/London";
  i18n.defaultLocale = "en_US.UTF-8";

  # ==========================================
  # 3. USER ACCOUNT (nimmo)
  # ==========================================
  users.users.nimmo = {
    isNormalUser = true;
    description = "Nimmo";
    # "docker" group allows running containers without sudo
    extraGroups = [ "networkmanager" "wheel" "docker" ]; 
  };

  # ==========================================
  # 4. HARDWARE & SERVICES
  # ==========================================
  # Framework 16 Fingerprint Reader
  services.fprintd.enable = true;
  
  # Connect Fingerprint to Auth Systems
  security.pam.services.sudo.fprintAuth = true;
  security.pam.services.kde.fprintAuth = true; # Lock Screen
  security.pam.services.sddm.fprintAuth = false; # Disable for login (KWallet)
  
  # Firmware & Updates
  services.fwupd.enable = true;
  hardware.enableAllFirmware = true; 
  hardware.cpu.amd.updateMicrocode = true;

  # Power Management (Standard: KDE Integration)
  services.power-profiles-daemon.enable = true;

  # SSD & Filesystem Maintenance
  services.fstrim.enable = true;
  services.btrfs.autoScrub = {
    enable = true;
    interval = "weekly";
    fileSystems = [ "/" ];
  };

  # Automatic Garbage Collection
  nix.gc = {
    automatic = true;
    dates = "weekly";
    options = "--delete-older-than 7d";
  };
  
  # Bluetooth
  hardware.bluetooth.enable = true;
  hardware.bluetooth.powerOnBoot = true;

  # Audio (Pipewire)
  security.rtkit.enable = true;
  services.pipewire = {
    enable = true;
    alsa.enable = true;
    alsa.support32Bit = true;
    pulse.enable = true;
  };

  # Docker Support
  virtualisation.docker.enable = true;

  # Steam (Ports & 32-bit dependencies)
  programs.steam = {
    enable = true;
    remotePlay.openFirewall = true;
    dedicatedServer.openFirewall = true;
  };

  # ==========================================
  # 5. DESKTOP (Plasma 6)
  # ==========================================
  services.xserver.enable = true;
  services.displayManager.sddm.enable = true;
  services.displayManager.sddm.wayland.enable = true;
  services.desktopManager.plasma6.enable = true;
  services.xserver.xkb.layout = "us";

  # ==========================================
  # 6. GRAPHICS (RTX 5070 + Strix Point)
  # ==========================================
  hardware.graphics = {
    enable = true;
    enable32Bit = true;
  };

  services.xserver.videoDrivers = [ "nvidia" ];

  hardware.nvidia = {
    modesetting.enable = true;
    
    # Power Management (Default: Finegrained/Battery Friendly)
    # This puts the GPU to sleep when not in use.
    # Note: Overridden to 'false' in Gaming Mode specialisation above.
    powerManagement.enable = true;
    powerManagement.finegrained = true;
    
    open = true;
    nvidiaSettings = true;
    package = config.boot.kernelPackages.nvidiaPackages.beta;

    prime = {
      offload = {
        enable = true;
        enableOffloadCmd = true;
      };
      
      amdgpuBusId = "PCI:194:0:0";  # c2:00.0 -> 194
      nvidiaBusId = "PCI:193:0:0";  # c1:00.0 -> 193
    };
  };

  # ==========================================
  # 7. NIX CORE SETTINGS
  # ==========================================
  nixpkgs.config.allowUnfree = true;
  nix.settings.experimental-features = [ "nix-command" "flakes" ];
  system.stateVersion = "24.11"; 

  # ==========================================
  # 8. POLISHING (Fonts & Compatibility)
  # ==========================================
  fonts.packages = with pkgs; [
    noto-fonts
    noto-fonts-cjk-sans
    noto-fonts-emoji
    nerd-fonts.jetbrains-mono 
  ];

  programs.nix-ld.enable = true;
  programs.nix-ld.libraries = with pkgs; [
    stdenv.cc.cc.lib
    zlib
    fuse3
    icu
    nss
    openssl
    curl
    expat
  ];

  environment.variables.EDITOR = "nano";
}